Without any fancy byte strings:
main = do
name:_ <- getArgs
file <- readFile name
print $ length $ lines file
On Thu, Sep 18, 2008 at 6:02 PM, Creighton Hogg
Hey Haskell, So for a fairly inane reason, I ended up taking a couple of minutes and writing a program that would spit out, to the console, the number of lines in a file. Off the top of my head, I came up with this which worked fine with files that had 100k lines:
main = do path <- liftM head $ getArgs h <- openFile path ReadMode n <- execStateT (countLines h) 0 print n
untilM :: Monad m => (a -> m Bool) -> (a -> m ()) -> a -> m () untilM cond action val = do truthy <- cond val if truthy then return () else action val >> (untilM cond action val)
countLines :: Handle -> StateT Int IO () countLines = untilM (\h -> lift $ hIsEOF h) (\h -> do lift $ hGetLine h modify (+1))
If this makes anyone cringe or cry "you're doing it wrong", I'd actually like to hear it. I never really share my projects, so I don't know how idiosyncratic my style is. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe